This invention relates to a method for diagnosing an optical device, and more particularly to a method for diagnosing both optical devices installed in a scanner section and a printer section that are incorporated in, for example, a digital copy machine.
Image forming apparatuses such as digital copy machines comprise a scanner section for optically reading a document image and creating image data, and a printer section for forming an image on a sheet of paper on the basis of the image data. The scanner section and the printer section each include an optical device equipped with a plurality of optical systems. Since the optical device is manually adjusted by a skilled worker in the manufacturing process of the image forming apparatus, lots of time is required for the adjustment of the optical device, and the adjustment precision is unstable.
In order to shorten the required adjustment time and stabilize the adjustment precision, research for expressing the amount of displacement with a numerical value by using an exclusive chart to realize automatic adjustment is now being made.
Japanese Patent Application KOKAI Publication No. 8-102818 discloses a method for detecting displacements in the main scanning direction and the sub scanning direction, and also detecting errors in magnification in these directions, using a mark that has its width linearly varied in the sub scanning direction and has an edge parallel to the main scanning direction. The detection method using such a mark, however, cannot detect another displacement or error.
Japanese Patent Application KOKAI Publication No. 5-75797 proposes a chart for adjustment that enables the detection of another adjustment item. However, in this method, a large number of detection marks must be used in the chart, a large number of detection positions are required, and lots of detection time is required.
Moreover, the conventional chart is only applicable to the adjustment of an optical device employed in the scanner section, but not to the adjustment of the entire image forming apparatus including the scanner section and the printer section.
In addition, in a so-called complex-type digital copy machine that has a fax function and/or a printer function as well as a copy function, the reading performance of the scanner section alone, the printing performance of the printer section alone, or the performance of the entire apparatus significantly influences the image quality realized by each function. Therefore, it is necessary to diagnose the performance of each section.
The present invention has been developed to solve the aforementioned problems, and is aimed at providing a method of diagnosing an optical device and capable of always providing stable image quality at low cost and using a simple system.
According to an aspect of the invention, there is provided a method of diagnosing an optical device having a plurality of photoelectric elements that are arranged in a scanning line in a main scanning direction, for receiving light reflected from a document and outputting a signal corresponding to an amount of light received, comprising:
a first step of reading, along a predetermined scanning line, a figure that consists of a first straight line perpendicular to the main scanning direction, second and third straight lines parallel to each other and intersect the first straight line at an acute angle, using the photoelectric elements of the optical device opposed to the figure with a predetermined space interposed therebetween;
a second step of detecting respective positions of first, second and third intersections between the scanning line and each of the first, second and third straight lines of the figure, and also detecting output levels of signals corresponding to the intersections, on the basis of signals output when the figure has been read along the scanning line; and
a third step of comparing the detected positions of the intersections with positions of respective predetermined points which are to detect the intersections, and the detected output levels of the signals corresponding to the intersections with respective predetermined output levels of signals corresponding to respective predetermined points, thereby detecting an error due to an attachment position of the optical device.
According to another aspect of the invention, there is provided a method of diagnosing an optical device installed in an apparatus that is equipped with reading means for reading a document image and storage means for storing reference data corresponding to a predetermined image pattern, comprising:
a first step of reading the predetermined pattern and converting the read pattern into image data, using the reading means; and
a second step of comparing the image data with the reference data stored in the storage means, thereby detecting a first image reading characteristic due to displacement of at least one component of the reading means from a predetermined position, and a second image reading characteristic due to deviation of a control parameter from a predetermined value, which occurs at the time of conversion to the image data.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.